Increasing use is being made of linear drive concepts as transport systems in production and manufacture, in which concepts a plurality of transport carriages can be controlled and moved independently of one another on a transfer path, thereby making it possible to achieve a high flexibility in product flow, e.g. in order to perform grouping of products or to allow for different process times. In designing linear drive systems, it has proven advantageous to form the transfer path from energizable magnetic field generators, whereas the carriages move passively in a wireless manner.
A linear drive system of this kind is described in DE 10 2012 204 919 A1. In this linear transport system, a series of magnet coils is arranged along the transfer path, wherein the carriages arranged on the transfer path are provided with permanent magnets. Dynamic activation of the individual coils along the transfer path produces a dedicated traveling field equivalent to a three-phase field for each carriage, which moves the carriage independently of the other carriages. Here, the transfer path together with the individual coils is of modular construction, and can also be embodied as a closed track in order to allow circulating transport.
In linear transport systems, however, movement is possible only in one direction along the transfer path. In a production and manufacturing process, however, a two-dimensional movement, particularly in the region of the workstation, is often required when transporting a workpiece to be processed. The required movement in the second direction is then generally performed by the workstation itself or by a robot or some other actuator associated with the workstation.
To enable a two-dimensional movement to be carried out, there is also the possibility of designing a carriage in a transport system as an XY table, also referred to as a compound table or compound rest. XY tables are two-axis systems comprising two single-axis linear guide systems, which allow movement of an object in two directions within one plane. The XY table carries the workpiece to be processed and can adopt any position within the XY plane through the interaction of the two axes as long as this position is within the capacity for movement of the guide. When an XY table is used in a linear transport system, however, it is necessary to implement a further axis drive on the carriage, e.g. in the form of a motor-driven screw or, alternatively, of a further linear motor in order to be able to perform a two-dimensional movement. However, the consequence of this is that the carriage can no longer be embodied in a passive wireless manner.
US 2009 010 78 06 A1 discloses an XY table of the type in question where an XY table has a carrying structure having two single-axis linear guide systems, which are embodied with an angular offset relative to one another. The two single-axis linear guide systems are each associated with a transport carriage. By a relative movement of the two carriages carrying the XY table relative to one another, the carrying structure can be moved transversely to the transfer path along the two linear guides.
KR 10 2003 006 756 A shows a linear transport system having two carriages, which bring about the movement of a support table through changes in the relative spacing thereof. WO 2011 131 385 A1 discloses linear carriages which can run along the side of a carrying structure.